1. Field of the Invention
The present invention relates to vapor compression systems for refrigerants, more particularly to fluid containment vessels in such vapor compression systems.
2. Description of the Related Art
Refrigeration systems typically include, in series, a compressor, a condenser, an expansion device, and an evaporator. In operation, gas phase refrigerant is drawn into the compressor where it is compressed to a high pressure. The high pressure refrigerant is then cooled and condensed to a liquid phase in the condenser. The pressure of the liquid phase refrigerant is then reduced by the expansion device. In the evaporator the low pressure liquid phase refrigerant absorbs heat and converts the low pressure liquid phase refrigerant back to a gas. The gas phase refrigerant then returns to the compressor and the cycle is repeated.
Compressors are typically designed for the compression of gas phase refrigerant, however, it is possible for a certain amount of liquid phase refrigerant to flow from the evaporator toward the compressor. For instance, when the system shuts down condensed refrigerant may be drawn into the compressor from the evaporator, thereby flooding the compressor with liquid phase refrigerant. When the system is restarted, the liquid phase refrigerant within the compressor can cause abnormally high pressures within the compressor and can thereby result in damage to the compressor. To prevent this phenomenon from occurring, it is known to use suction accumulators in the refrigeration system in the suction line of the compressor.
Commonly used suction accumulators are mounted near the suction inlet of the compressor and separate liquid and gas phase refrigerant. As the refrigerant flows into the accumulator, the liquid phase refrigerant collects at the bottom of the storage vessel, while the gas phase refrigerant flows through the storage vessel to the compressor. Typically, a metered orifice is provided in the lower portion of the vessel to dispense a small amount of the collected liquid phase refrigerant to the compressor, thereby preventing large amounts of potentially harmful liquid phase refrigerant from entering the compressor.
When the system is shutdown, thermal energy is transferred from the ambient environment to the refrigerant in both accumulator and the evaporator, thereby warming the refrigerant therein. Because the evaporator comprises a large mass of metal and ice often accumulates on the evaporator surface, the evaporator tends to warm up more slowly than the accumulator. The refrigerant has a natural tendency to migrate to the coolest area of the system, when not subjected to suction pressure and, therefore, the refrigerant is attracted to and naturally migrates to the evaporator. However, the heat exchangers of a refrigeration system, including the evaporator and condenser, typically comprise many folds or joints. These joints are more vulnerable to developing leaks relative to components not having joints. Accordingly, when leaks occur in the system, they most commonly occur in either the evaporator or the condenser. It would be beneficial to trap the refrigerant in a special storage vessel during shutdown to thereby contain the refrigerant, prevent it from migrating to the evaporator and minimize the possibility of leaks.